JPH05270214A - Pneumatic tire with large resistance against eccentric wear - Google Patents

Abstract

PURPOSE:To provide a tire with a block structure which can avoid in favorable performance the heel-and-tow wear of the block pattern on the tire. CONSTITUTION:The cylindrical crown part of a pneumatic tire is provided with a tread, which includes a plurality of circumferential grooves 1 stretching along the equator of the tire and blocks each bounded by a number of crosswise grooves 2 extending across these circumferential grooves 1, and with this tire the rotating direction is specified unidirectionally. The block is so arranged as to meet the condition alpha>beta, where alpha is intersecting angle of the grounding surface 4 of block 3 with the stamp-in side wall surface facing the crosswise grooves 2 and beta is the intersecting angle of the grounding surface with the kick-out side wall surface 5 facing the crosswise grooves 2, and these angles alpha, beta, the width (a), length (b), height L of the block 3, and the block stiffness associated with the Young's modulus of rubber are put in the range 0.07 to 0.20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a tread having excellent uneven wear resistance.

[0002]

2. Description of the Related Art Ribs, blocks or lugs are provided on a tread arranged on the crown portion of a tire. Among them, the block pattern is often used for truck and bus tires because of its high drainage property. ing.

In the block pattern, usually two to five circumferential grooves extending along the equator of the tire are arranged at a predetermined interval, and a large number of lateral grooves extending in a direction traversing the circumferential groove are arranged at substantially equal intervals. The block is defined by the circumferential groove and the lateral groove and both ends of the tread. And the circumferential groove is
In addition to straight lines, there are various types such as zigzag and crank shapes,
On the other hand, the lateral groove has a predetermined inclination angle with respect to the equator of the tire,
It is customary that the cross section is formed in a V or U shape, and both wall surfaces of the block facing the lateral groove stand up from the bottom of the lateral groove at substantially the same angle.

[0004]

A problem when this block pattern is applied to tires for trucks and buses, which are used on pavements, especially under high internal pressure and heavy load, is a so-called heel and toe. Uneven wear, called wear. Here, heel and toe wear is
In each block arranged along the circumferential groove, the side to be grounded first during traveling, that is, the end on the stepping side,
This is a phenomenon in which the end on the side that comes in contact with the ground later, that is, the kick-out side, is worn early and becomes unevenly worn. When this heel-and-toe wear occurs, the appearance is deteriorated and the tire life is shortened.

Therefore, an object of the present invention is to propose a block structure capable of advantageously avoiding heel-and-toe wear in a block pattern.

[0006]

According to the present invention, a tread is arranged on a cylindrical crown portion, and a plurality of circumferential grooves extending along the equator of a tire are provided on the tread, and a plurality of circumferential grooves extending in a direction crossing the circumferential grooves. A pneumatic tire having a block partitioned by the lateral grooves of the tire, the tire rotation direction of which is specified in one direction, in which the intersection angle α of the ground contact surface and the stepping side wall surface facing the lateral groove, and the ground contact surface And the crossing angle β of the side wall surface of the protrusion facing the lateral groove is α> β
And the block rigidity k represented by the following formula (1) is in the range of 0.07 to 0.20, the pneumatic tire having excellent uneven wear resistance.

[Number 2] Symbol k = (E · V · W ) / (L 3 · X) ---- (1) However, V = 2 {(tanα + tan β) / 2} 3 L 3 +4 {(tanα + ta
n β) / 2} ² L ² b + 3 {(tan α + tan β) / 2} Lb ²
+ B ³ W = cos ⁵ {(α-β) / 2} X = 2b-Ltan {(α-β) / 2} where a: tire axial width of the block (mm) b: block tire circumferential direction Length (mm) L: Height from lateral groove bottom of block (mm) E: Young's modulus of rubber (kgf / mm ² ).

Now, FIG. 1 shows a main part of a tread of a pneumatic radial tire to which the present invention is applied. A plurality of circumferential grooves 1 extending along the equator of the tire and arranged substantially parallel to each other and spaced apart from each other, and the circumferential grooves 1
Each of the blocks 3 forming a column block group of 5 rows is divided by the space or the circumferential groove 1 and a large number of horizontal grooves 2 connecting the tread ends T.

Here, each block 3 is shown in FIG.
-As shown in the cross section along the line A, the ground plane 4 and the lateral groove 2
Angle α of the wall surface 5 on the stepping side of the block facing to the wall surface 6 on the kicking side of the block facing the contact surface 4 and the lateral groove 2
It is essential that the crossing angle β of is in a relation of α> β. Further, these intersection angles α and β, the width a, the length b, the height L, and the Young's modulus E of the rubber in each block 3
With regard to and, the block rigidity k expressed by the above equation (1) is
It is necessary to design the block so that the range is 0.07 to 0.20.

In the block 3 thus designed, the stepping side and the kicking side are strictly distinguished from each other. Therefore, even when the tire is used, it is necessary that the rotation direction of the tire is always the same when the vehicle goes straight. Therefore, the direction of rotation of this tire must be specified in one direction. That is, when the tire is mounted on a vehicle, its direction is limited, and in such a tire, the lateral groove 2 forms an acute angle with the circumferential groove 1 and is oriented toward the equator of the tire (vehicle traveling direction). The arrangement that extends to is particularly advantageous in improving drainage.

Therefore, FIG. 3 shows an example of a block pattern in which the limitation of the tire rotation direction is positively utilized. As described above, the block pattern shown is one in which the lateral groove 4 is inclined with respect to the circumferential groove 5 so as to have a substantially arrowhead-shaped arrangement as a whole, and the rib 7 with the notch 6 is provided at the center of the tread. The blocks 8 and 9 each having a diamond shape or a combination of diamond shapes are defined on both sides thereof. Also in this block pattern, it is important to design a block that satisfies the relationship of α> β and that the block rigidity k is in the range of 0.07 to 0.20.

Here, in the block shown in FIG.
When adapting (1), it is difficult to determine the length b of the block in particular, but in such a polygonal block, the area S of the ground plane of the block is determined, and this area S is defined by the width a of the block. The value obtained by dividing is set as the length b.

In the present invention, it is not necessary that the entire surface of the tread be a block, and it goes without saying that the pattern shown in FIG. 3 in which ribs are combined with the block may be used. However, since heel and toe wear is likely to occur near the tread edge, it is particularly advantageous to apply the present invention to a pattern in which a row of blocks is arranged in an area adjacent to the tread edge.

[0013]

The present inventors have made various studies on heel-and-toe wear and found that when the rising angle from the lateral groove bottom of the wall surface facing the lateral groove of the block is the same on the stepping side and the kicking side, Sometimes when each block reaches the contact area, the end of the stepping side is first compressed and deformed,
The compression deformation remains as compression or contraction deformation of the block in the tire circumferential direction over the range between the stepping side end and the kicking side end after the kicking side end contacts the ground. The compression or contraction deformation of this block lasts until the block separates from the contact area, and is largely accumulated particularly in the kick-side end region, and when the block is separated, slippage between the road surface and the kick-side end part occurs. Occurs. If this sliding is repeated and wear occurs, and the kick-out side end part is locally worn out early, the ground contact pressure here becomes lower than that of the other parts of the block, so the kick-out side end part Moves easily in the contact area and promotes early wear of this portion, and a large wear step, that is, heel and toe wear occurs between the end on the stepping side and the end on the kicking side.

Therefore, when each block reaches the contact area by satisfying the relation of α> β and setting the block rigidity k represented by the above equation (1) within a predetermined range. It is possible to suppress the compressive deformation of the stepped side end portion. Then, since the deformation that occurs when the foot end reaches the contact area spreads over the entire block, it is possible to suppress slippage that occurs when the kick-out end separates from the contact area, and the heel and Toe wear can be advantageously avoided.

That is, if the intersecting angles α and β are in a relation of α ≦ β, the compressive deformation is likely to be locally generated only near the stepping end, and as a result, a large slip is caused in a wide region of the kicking end. In order to cause a disadvantage to occur, it is necessary to first set α> β.

Next, the block rigidity k expressed by the above equation (1) is set to the range of 0.07 to 0.20 because when k is large,
Deformation is locally accumulated, resulting in the disadvantage that the kicking end is generally slippery in a wide area, while when k is small, it is good that the deformation spreads out in the block circumferential direction, This is because the deformation of the kick-out end when it is separated from the ground is large and may be damaged. Tire No. 5 described later is an example. As a result, the heel-and-toe performance is degraded due to wear due to breakage. The proper range is 0.07 ≦ k ≦ 0.20 according to the indoor test.
Turned out.

[0017]

EXAMPLES Pneumatic radial tires for trucks and buses having a tire size of 11 R 22.5 were prototyped according to the tread pattern shown in FIG. That is, the circumferential groove of the tire is 7.
The width was 0 mm and the depth was 15.0 mm, the lateral groove was 7.0 mm and the depth was 10 to 15 mm, and the blocks were various shapes according to Table 1.

The test tires produced for each of these block types were assembled into rims of size 7.5 x 22.5, respectively.8.
After setting the internal pressure to 5 kgf / cm ² , this wheel was installed as a front wheel of a truck, and it was used on a paved road mainly composed of highways to reach 30,000
After traveling for km, the difference in wear between the stepping side end and the kicking side end of each block was measured. The measurement results are shown in Table 1 as an average value.

[0019]

[Table 1]

From the table, tire Nos. 1 and 2 are α ≦ β
And tires Nos. 4 and 5 have block rigidity k
Since it is out of the range of 0.07 to 0.20, it can be seen that the wear step is large as compared with the tire No. 3 satisfying the present invention.

[0021]

According to the present invention, heel-and-toe wear in a block pattern can be advantageously avoided, and tire life can be significantly extended.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a block pattern to which the present invention is applied.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a schematic diagram showing ribs and block patterns to which the present invention is applied.

[Explanation of symbols]

 1 circumferential groove 2 lateral groove 3 block 4 lateral groove 5 circumferential groove 6 notch 7 rib 8 block 9 block

Claims (1)

[Claims] 1. A block in which a tread is arranged on a cylindrical crown portion, and a plurality of circumferential grooves extending along the equator of a tire and a plurality of lateral grooves extending in a direction traversing the circumferential grooves are defined on the tread. And a crossing angle α of the stepping sidewall surface facing the ground contact surface and the lateral groove in the block, and the kicking side facing the ground contact surface and the lateral groove. A pneumatic tire having excellent uneven wear resistance, which has a relationship of α> β with a wall surface intersection angle β, and has a block rigidity k represented by the following formula in a range of 0.07 to 0.20. [Expression 1] Note k = (E · V · W) / (L ³ · X) where V = 2 {(tan α + tan β) / 2} ³ L ³ +4 {(tan α + ta
n β) / 2} ² L ² b + 3 {(tan α + tan β) / 2} Lb ²
+ B ³ W = cos ⁵ {(α-β) / 2} X = 2b-Ltan {(α-β) / 2} where a: block tire axial width (mm) b: block tire circumferential direction Length (mm) L: Height from lateral groove bottom of block (mm) E: Young's modulus of rubber (kgf / mm ² )